This invention relates to digital communications and, more particularly, to channel and entropy coding.
In digital communication, source information is quantized into bits and entropy-coded into code-words of variable length. This process is generally called redundancy reduction in speech, still image and video. See A. K. Jain, xe2x80x9cFundamentals of Digital Image Processing,xe2x80x9d published by Prentice Hall, 1989. The entropy-coded symbols are added with controlled amount of redundancy, which is generally called channel-coding. See R. E. Ziemer and W. H. Tranter, xe2x80x9cPrinciples of Communication Systems, Modulation and Noise,xe2x80x9d published by Houghton Mifflin, 1995. The resultant sequence of binary data is converted into analog, modulated and transmitted on an RF carrier.
The received signal is demodulated into base-band signal, which is again converted into digital for channel decoding, through which, using the redundancy added at the transmission side, errors that occurred are corrected. The resultant sequence of binary data is then decoded into source code-words by mapping binary data segment into an element of a variable code.
In the standard implementation of a communication system, channel decoding and entropy decoding are treated as separate function blocks because their counterparts, entropy encoding and channel encoding, are treated separately.
In this application, it is taught that a new combined implementation of channel and entropy decoder significantly improves the transmission bit-error rate. The gained improvement is due to the use of maximum-likelihood information generated by the channel decoder and the intrinsic property of the variable-length codes that the code-lengths are variable.